Background

(TODO: Shawn ? Here we need to put some quick intro on the value of a DVCS, and present a bit the field.
I am sure Shawn has some good slides on that, he had made a presentation @ the GSOC mentor summit that we could extract some bits from.
Traditional source code version control systems .....
)

Introduction

The EGIT plugin is an Eclipse Team provider for Git (a.k.a. "Stupid Content Tracker", http://git.or.cz).

Git is the version control system originally developed for the Linux kernel by Linus Torvalds, and is now a general Source Code Management (SCM) tool. One of the Git strength is its ability to support distributed version tracking as well as more centralized schemes, in contrast with tradition SCM that offer only a centralized model (such as CVS and Subversion) and to be very fast.
Beyond the Linux kernel team, Git is now used by many other projects, both for open source and commercial development.

Git is a distributed SCM, which means every developer has a full copy of all history of every revision of the code making queries against the history very fast and versatile. The storage model also means most operations are ten to a hundred times faster than with traditional centralized SCM such as CVS or Subversion. The integrity of the code is guaranteed through the use of secure hashes on the content and history, plus optional GPG(PGP) key signing of tags.

Project Goal

The goal of the EGit project is to:

implement an Eclipse Team provider for the Git SCM,

work towards the definitions of new Team extensions and GUI paradigms to better support distributed SCM in general.

Project Scope

The project will implement Eclipse tooling for the JGit Java implementation of Git.
Specific attention will be focused on performance. Performance is a big deal with Git. It affects what can be done by being so much faster. Things that couldn't be done because of time constraints are now possible. These things like very fast checkouts, branching, branch switching, merging, tagging, software archeology and synchronization. Merge speed is probably the most important feature.
The EGit plugin meta data shall be fully compatible with the meta data created by the native Git version so both can be used on the same checkout out repository.

Beyond the Git support implementation, the project will work towards defining new essential extensions to the Eclipse core platform Team framework to account for the specific issues and features provided by distributed version control systems.
It is also our intent to reach out to other project that implement support for distributed SCM in Eclipse to collaborate and exchange in that domain.

Finally, the implications of adopting a distributed SCM approach can bring significant benefits especially for large open source projects such as Eclipse and can help lower the barrier to entry for new contributors and source code experimentation easier.
The project will try to be a fervent advocate of distributed SCM benefits to the Eclipse community.

Project description

The Git team provider will provide the ability to do all everyday task in a Git work flow from inside Eclipse, integrated with the Eclipse Team framework, and providing new features specific to Git and distributed version control management.

Features

Initial project setup: Support to create new Git repositories.

Importing existing code: Existing local Git repositories as well as remote repository can be imported. Remote repositories are imported by "cloning" them resulting in a local copy.

Replicating repositories: It shall be possible to distribute local version to other repositories through "push" operations as well as patches distributed by electronic mail. Receiving content shall be possible by fetching content via the git supported protocols (raw, ssh and http based) and via e-mailed patches directly from mailboxes, files or clipboard. "Bundles" shall also be supported.

Quickdiff against any version shall be supported.

Comparing any versions shall be supported.

Producing git-format patches to the clipboard shall be supported.

Selective commit (using the Quickdiff markers) shall be supported

Merge shall be supported

Cherry picking shall be supported

Re-base of branches shall be supported. This includes splitting, reordering and squashing (alternate term not to be confused with the normal meaning of "merge" in SCM terminology).

Some form of synchronization with CVS or other SCM. At least export to CVS, like git cvsexportcommit. Ideally Git commits shall be exportable to a CVS repository with the same structure. CVS import is a much harder problem where no perfect solution exists.

Perspective and Views

A Git perspective will be provided for browsing repositories before importing Git projects, pre-configured with available Team views and new EGit views.

History viewer: An history viewer with graphical presentation of history and access for compare editors will be developed as well as other views that may be useful for distributed SCM.

Repository browser : An explorer for examining Git repositories not connected to an eclipse project. Importing projects shall be possible from here.

Global directory: An explorer to find manage Git repositories ( at the minimum minimum all known local clones and their "remotes")

Extension points

Quickdiff must be enhanced to allow selective committing.
New extensions points will be designed as needed to expose new core extensibility common to many distributed SCM.

Extensions to existing Eclipse Team functionality

Team provider
Resource decorators
Quickdiff provider

Organization

We propose this project should be undertaken as an incubator project with the Technology project.

Mentors

The following members of the Eclipse Architecture Council have kindly agreed to mentor this project:

Chris Aniszczyk

Andrew Overholt

Initial Committers

Robin Rosenberg (project lead)?

Shawn Pearce (project lead) ?

Philippe Ombredanne

(TODO: Robin: what about others?)

Initial Code Contribution

The initial code contribution is based on the existing EGit code base licensed under the EPL. (this has already been approved by current comitters).
(TODO: Robin+ Shawn: get complete email approval from all the committers for both EGIT and JGit for anyone that contributed to the code base that will be contributed)
(TODO: Robin+ Shawn: update all copyright headers in the code)

Licensing and Intellectual property

A point of note is that EGit depends on the JGit, a pure Java Git implementation of Git.
JGit was originally licensed under a combination of GPL and LGPL and is now made available under a (BSD/Apache/MIT TBD) license. The developers of JGit are also the original developers of EGit.
(TODO: Robin+ Shawn: pick license of JGit, and add header to JGit)

Now Git itself is licensed under the GPL V2, but JGit is a clean implementation of the core Git data structures and as such has received the approval of the core Git maintainers (including LT, (TODO: Robin+ Shawn+Phil: get email confirmation from Linus + current lead maintainer on that topic)
) to be licensed under any open source license the authors wish. Therefore the JGit authors have elected to license JGit under the (Apache/BSD/MIT TBD) license which is compatible with the Eclipse Public License.
As part of the original code contribution review, JGit will be also submitted for approval per the Eclipse development process.
(TODO: Robin+ Shawn: get complete email approval from all the committers for both EGit and JGit for anyone that contributed to the code base that will be contributed)

Interested Parties

TBD
(TODO: all list interested individual and companies ....)

Ismael Juma

Neil Bartlett

Chris Aniszczyk

User community

EGIt and JGit already have an established community and we expect that this community of users and contributors will join this new project at Eclipse. Of note is that the general support of Git on Windows is limited. By being platform neutral, EGit has the opportunity to provide advanced Git support also on this platform and serve the needs of a larger community.

Relation to other Eclipse projects and to other open source projects

(TODO: Robin:review and add a few words for possible project we intersect with)

Mylyn - a Task based IDE that provides privileged integration with Eclipse-supported team providers . A possible integration with EGit could be considered.

Buckminster

Tentative Development plan

Some functionality already exists, but there is no real plan at the moment for lack of committed resources. The project's rough priorities are:

Already done:

Connect to/create repositories for exiting projects

Create branches

Commit

Quickdiff against current revision

Resources decorators for tracked and modified resources as well as repository state

Basic compare of revisions

Underway:

Cloning and updating from remote repositories

Future:

Bisecting

Partial commits (i.e. committing partial changes)

Comprehensive handling of different character encodings in filenames and comments.

CRLF handling (unless we consider it unneeded)

Bugfixes for existing code

Formatting code for patch submission through e-mail

Apply patch

Rename/Copy tracking in compare revisions

Blame (annotate)

Merge

Rebase

External repository browser

Repacking (this a really a core Git feature and the one that can be really hard or impossible to perform in Java).

Rename tracking is an on-demand feature in git. Git does not record such information, it discovers it from content. The tight data structures in git makes implementing this in real time possible, but could still be a challenge.